What makes a piano go out of tune?
Your piano’s worst enemy is fluctuation in humidity. During humid months, the soundboard in your piano swells and exerts extra tension on the strings, which makes them go sharp. In the drier months, the soundboard dries out and shrinks, releasing some tension on the strings, causing your piano to go flat. Contrary to popular belief, it is not moving a piano, excessive play, or no play at all that makes it go out of tune.
